Squashed 'brjs-sdk/workspace/sdk/libs/javascript/browser-modules/' changes from cd2da00..4970a74

4970a74 1. Fixed a bug that meant we continued to use state related to the realm where an object was first created, even though a sub-realm had been installed. 2. Added lots more spec tests around realm and sub-realm installation and use. 3. Cleaned up the existing spec tests. 4. Simplified the code, and pulled out the code used to define the require-function passed to defined modules to make things clearer.

git-subtree-dir: brjs-sdk/workspace/sdk/libs/javascript/browser-modules
git-subtree-split: 4970a74e28a345ebf81564bc7fb746ae49ef3aeb
Merge commit '09bbcf9cd11b3e8e802d5f498a1f4fbe4a1b96da' into better-client-side-circular-dependency-handling